Poly thermal transitions associated with

With heating from 5 to 45°C, thermal changes in conformation in the major /3-casein are observed by spectral methods (Garnier 1966). From measurements of the optical density at 286 nm and of the specific optical rotation at 436 nm, a rapidly reversible endothermic transition (AH 30 kcal/mole) with a half-transition temperature of 23-24°C is observed. The optical rotatory dispersion data suggest a decrease in the poly-L-proline II structure (12 to 5%) and a slight increase in a-helix (11 to 16%) with increasing temperature. This transition probably occurs prior to association, since it is rapid, and the carboxyacyl derivative of the monomer, which does not polymerize with increasing temperature, also demonstrates the optical rotatory disperson thermal transition. 

DSC and DTA. They can be used to confirm suspicious glass transitions revealed by DSC and most important, they can further quantify molecular mobility associated with sub-glass transitions. For example, DSC analysis of poly (ethylene 2,6-naphthalene dicarboxylate) (PEN) only revealed the presence of a glass transition around 112 °C (Hardy et al., 2001). DMA analysis of the same sample, however, revealed two secondary relaxations below this glass transition (Hardy et al., 2001). In the case of humic materials, it is not uncommon for DSC to fail to detect clear thermal transitions due to their heterogeneous nature, which contributes to overlap/ broadening or washout of thermal transitions. As such,TMA and DMA represent powerful, complementary tools to DSC. 

In the present research, variables associated with physical aging near the alpha transition were used to examine the beta transition of a poly(amide-imide). After sample drying, the relationship between the beta transition s activation enthalpy and thermal history was explored. 

Of particular interest are phenomena associated with two thermally induced transitions 1) glass transition, and 2) melting of side group aggregates observed for example in PDHS at 315K14-17 and other poly(n-... 

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